Using isolated, in vitro neuroendocrine systems, to characterize membrane receptors on the specialized cells of these systems, then to study the various modulatory influences that may quantitatively alter receptor-mediated response, then to begin to understand stimulation- secretion coupling in these systems. The major systems to be studied are the supra-optic nucleus and the pineal of the rat, although it is hoped eventually to include systems involving ependymal and hypendymal elements.